Mercury relay



U. ME C. HEDIN F. RCURY ELAY ed April 4 194 'Ily Patented Dec. 1, 1942 MERCURY RELAY Uno C. Hedin, Des Moines, Iowa, assignor to Bucklen-Bear Laboratories, Inc., Elkhart, Ind.,

a corporation of Indiana Application April 4, 1941, Serial No. 386,821

12 Claims. (Cl. 200-9'7) This invention relates to mercury relays, and more particularly is concerned with improvements in the arrangement of the relay within a metal envelope and the provision of improved sealing means and particular construction of time delay means for controlling the operation of the relay.

Primarily, the present invention is concerned with a mercury relay formed from a cup-shaped metallic shell which forms one terminal or electrode of the relay and which has sealed in the open end thereof a second electrode projecting into the shell, the second electrode being of a construction allowing for the evacuation' of the elay and lling of the envelope with an inert gas under pressure.

In its preferred form, the present invention contemplates an electr-ode having an axial bore therethrough adapted to communicate with the interior of the shell and arranged at its outer end for connection to a suitable source of vacuum and of an inert gas such as hydrogen. The electrode may be formed of iron, cold rolled steel, or the like, and if desired, may carry in its inner end lan electrode tip portion formed of tungsten or a similar arc-resisting metal.

In another form of the invention the electrode is formed by the welding together of two metal tubulations.

Another object of the present invention is to provide a time delay element carried in the displacer which surrounds the second electrode, and

is arranged for axial movement within the envelope. This displacer is preferably formed with a lower end portion aldapted to carry a suitable time delay disc or discs arranged to meter the flow of mercury within the relay into the space within the displacer, thereby, in effect, metering the rate at which the mercury ilows through the displacer up into contact with the electrode tip. This determines the time between actuation of the energizing circuit and making of the Contact in the relay circuit.

The time delay elements employed may be of various forms, but I have found that the most desirable is the combination of ya plurality of discs which are of conical shape and arranged in opposed relation with a layer of mercury lying above the orifice in the lowermost disc for determining the time delay upon making of the circuit. Other forms which have been found acceptable are a at disc with a single aperture and a double tapered disc having an axial orifice.

Other objects and advantages of the present invention will Iappear more fully from the followtion with the accompanying drawing, will disclose.

to those skilled in the art the particular construction and operation of a preferred form of the present invention.

' In the drawing:

Figure l is a vertical sectional view through one form of the present invention;

Figure 2 is a detailed sectional view of the form shown in Figure 1;

Figure 3 is a corresponding sectional view of a modified construction;

Figure 4 is a sectional view through one form of a time delay element;

Figure 5 is a corresponding view of another form of time delay element;

Figure 6 is a view of another form of time delay element; and

Figure 7 is a vertical sectional view of a relay embodying a modied form of electrode construction.

Referring now in detail to the drawing, a cupshaped metal envelope is indicated generally at 5, and is provided with the enlarged open end 6 joined to the body portion by the shoulder 'I. Disposed within the open end of the envelope and seating against the shoulder I is `a refractory insulating member 8, which has an axial bore therethrough provided adjacent its outer radial face with the counterbore 9 and with a reduced annular shoulder Ill. Disposed in the counterbore 9 is the ange portion I2 of a tubular electrode I3, this electrode having the axial bore I4 extending therethrough and provided with the radial opening I5 adjacent the inner end of the ceramic 8. The shoulder or ange I2 of the electrode forms a seat limiting inward movement of the electrode I3 relative to the ceramic 8. 'I'he outer radial face of the shoulder I2 and the refractory 8 is adapted to be engaged by the resilient sealing gasket I 6, which is provided with aperipheral skirt portion II seating about the reduced shoulder I!) of the refractory.

The inner end of the electrode is provided with the counterbore I9, as indicated in Figure 2. adapted to receive the tungsten element 20 which may be pressed thereinto or held in the counterbore in any suitable manner. It will be noticed that the counterbore does not extend to the radial passageway I5, consequently leaving this passageway open into the axial bore I4.

Disposed against the outer radial face of the gasket I6 is a second resilient gasket 22 which is also provided with a peripheral flange portion 23 and with a centr-a1 annular flange 24 fitting about ing detailed description which, taken in conjuncthe annular surface of the electrode I3 above the flange I2. A refractory compression member 25, which may be formed of a ceramic material or may be a molded insulation or the like, is pressed inwardly against the gaskets 22 and I6, expanding the same into sealing engagement with the inner wall of the enlarged portion 6 of the envelope, and also about the annular surface of the electrode I3. The compression member 25 is held in compressed position, and a retaining washer 26 is placed thereon over which is spun the end 21 of the envelope to retain all the parts in compressed position, thereby providing an effective seal for the electrode I3. The outer axially eX- tending portion 28 of the compression member forms an insulating spacer radially between the spun-over end 21 of the envelope and of the electrode I4, and is preferably provided with an axial recess 29 in which is fitted a brass bushing 30.

The electrode I4 is provided with a reduced portion indicated at 32, and after the envelope has been iilled with mercury, as indicated by the body of mercury 33, and the parts have been placed in position and sealed, the outer end 33 of the electrode is connected to a suitable vacuum pump or the like for withdrawing al1 air, moisture and occluded gases from the interior of the envelope, after which the end of the electrode is connected to a source of hydrogen gas under pressure, which gas is :forced into the interior of the envelope. The reduced portion 32 of the electrode is then pressed together, closing off the bore I4, a-nd is suitably welded to provide an effective seal closing the interior of the envelope against escape of gas. A suitable stranded conductor 34 is then placed about the welded portion 35 of the electrode, the outer end of the electrode having been broken olf previously and the brass bushing placed in position. The flexible lead is then soldered to the projecting portion 35 of the electrode within the bushing to provide a positive electrical and mechanical connection of the conductor to the electrode.

Also disposed within the envelope is a displacer comprising an insulating sleeve 3E enclosed within an outer metal sleeve 31 forming an armature and subjected to magnetic action. The outer sleeve 31 has its upper end turned inwardly, as indicated at 38, to form an abutment for the ceramic sleeve 36. At the lower end a suitable time delay disc 33 is disposed across the lower end of the ceramic 3S and held in position by spinning over the lower end 43 of the shell 31. This locks the disc 39 in position, and provides an effective closure for the lower end of the displacer 31.

As will be noted in Figure 4, the disc 39 is apertured as indicated at 42, the size of the aperture being related to the thickness of the disc in such manner as to meter the flow mercury therethrough, whereby when the armature 31 is drawn downwardly by the energizing coil, mercury flows through the aperture 42 at a predetermined rate, filling the interior of the displacer until such time as the level of mercury has been raised to a point effecting contact with the element 20. This completes the relay circuit from the shell to the electrode I3, thereby energizing the control circuit in which the relay is Connected.

It will be noted that in the normal position of the displacer 31, when energized, there is a slight amount of mercury lying above the disc 39 within the displacer. This is for the purpose of preventing air locking but the disc 39 is not entirely effective in preventing the formation of gas bub- 75 bles which, to some extent, vary the time delay action of the disc.

In Figure 3 I have disclosed substantially the same structure in which corresponding parts are identied by similar reference numerals. However, in this form of the invention the displacer 31 is provided with a different type of time delay at the lower end thereof. This time delay is shown more in detail in Figure 6, and comprises two discs 48 and 49 which are brazed or suitably secured together adjacent the peripheral anges 50 and 52, forming a substantially double tapered or wedge-shaped displacer secured between the lower end of the insulating sleeve 36 and the spun-over edge 4Q of the displacer sleeve 31. The two discs 48 and 49 are each provided with central apertures, indicated respectively at 53 and 54. The aperture 54 is smaller than the aperture 53, and the size of aperture 54 controls the effective time delay between energization of the coil 2| and the making of contact between the shell 5 and the electrode tip 2U.

The time delay element shown in Figure 6 is superior to that shown in Figures 4 and 5 due to the fact that the interior or chamber formed between the two discs and indicated at 55 is filled with mercury. This allows the top disc to be provided with a relatively large hole without affecting the layer of mercury laying over the small hole 54. The hole 54 provides the time factor and by providing the larger hole in the upper disc, no air-lock can take place due to the fact that any air which might be trapped in the chamber 55 will be dispelled through the larger opening 53, which preferably is substantially larger than the meniscus length of mercury. The relatively thin disc provided with the small aperture 54 allows mercury to flow through this aperture even though it is smaller than the meniscus length of mercury, since there is mercury on both sides of the opening and there is no question of surface tension. Thus, the time delay element shown in Figure 3 provides a positive control of the time delay between energization of coil 2! which moves displacer 31 downwardly into the body of mercury 33 and the making of contact between the body of mercury and the electrode tip 29.

In Figure 5 I have disclosed a third form of time delay which comprises a double tapered solid disc 50 having a peripheral flange portion 32 adapted to be secured between the lower end of sleeve 36 and the spun-over end 43 of the displacer 31. The disc is provided with a bore '53 extending therethrough, but if the relay is tilted sufficiently to uncover this hole, momentarily within the displacer, there is a possibility of air locking of this structure, requiring a greater pressure for the mercury to break through the aperture 63 and rise within the displacer. Consequently, the time delay of such an element, while desirable, is not as perfect as that of an element where there is a constant layer of mercury on both sides of the aperture at all times. By providing the chamber 55, as shown in Figure 6, the mercury cannot spill out but is trapped so as to always lay over the top of the opening 54.

In Figure 7, I have disclosed a modified electrode construction for a mercury relay, this electrode construction comprising a first tubulation 10 having a flanged end 12 which is welded or otherwise suitably secured within a correspondingly shaped opening in a solid disc 13. A second tubulation 14 corresponding to that shown at 10 is also provided with the corresponding anged end 15 secured in the disc 16.

The two discs are then disposed in `face to face relationship, and are suitably welded together as at 11, providing a tubular electrode with an intermediate annular flange adapted to set in a suitable recess in a refractory plug 18. The yplug "I8 seats against the shoulder 19 of a metal envelope or shell 8U, which in turn has a coil diagrammatically shown at 82 about the lower end thereof. A suitable displacer 3l is provided which may carry at its lower end any one `of the time delays shown in Figures 4 to 6, being illustra-ted with the elements shown in Figure 5. The tubulation is provided at the point where it projects inwardly beyond the plug i3 with an opening 83, which opening is similar to the radial port l5 shown in Figures 1 and 3. This opening provides for evacuation of the interior of the envelope 8U through the tubulations Hl and 14 in the same manner as previously described. Preferably, the lower tubulation 'IIJ is also provided with the arc resisting electrode tip 84 similar to the tip of Figures 1 and 3. Suitable gaskets 85 and 86 are provided which are adapted to be radially expanded by a suitable compression member with the end of the envelope then sealed over in the same manner as described in connection with Figures 1 and 3.

The relay shown in Figure '7 is illustrated in a partially assembled form before the introduction of the compression member and the spinning over to seal the mechanism in position. However, its operation is the same as described in connection with Figures 1 and 3 when completely assembled.

It is therefore believed apparent that I have provided a novel type of mercury relay having certain added features of electrode construction, sealing engagement and time delay elements which provide a positively operating relay that may be provided with any predetermined time delay, and which may be readily and economically assembled and is susceptible to mass production. It is to be understood that the envelopes 5 and 8l! are preferably formed of austenitic steel so that the coils will have direct influence on the displacers with the shells interposing no magnetic reluctance. It is also to be understood that by reason of the tubular electrode construction which allows evacuation and lling with hydrogen under pressure, the possibility of arcs within the envelope is materially reduced, and also, the mercury is maintained free of oxidation and the contacts are prevented from pitting or corrosion, thus adding long life and positive operation to the relays. Y

I am aware that various changes may be made in certain details of the present construction, and I therefore do not intend to be limited except as defined by the scope and spirit of the appended claims.

I claim:

1. In combination, a cup-shaped metal envelope having an enlarged open end, a ceramic seated in said end, an electrode extending through said ceramic and having an intermediate collar portion, a recess in the outer face of said ceramic receiving said collar portion, resilient gasket means engaging over said electrode and having peripheral iianges extending in opposite directions, compression means axially engaging said gasket means, a spun-over end on said envelope locking said compression means in position, a body of mercury in said envelope, and magnetically responsive means in said envelope for displacing mercury into contact with the inner vend of said electrode.

2. The combination of claim 1 wherein said electrode is tubular and has a radial opening beyond the inner face of said ceramic allowing evacuation and filling of said envelope with an inert gas through said electrode.

3. In a metal envelope mercury relay, a'displacer having a ceramic sleeve, a paramagnetic outer sleeve thereover having an inturned radial flange at one end thereof, and disc means having its periphery retained between the end of said ceramic sleeve and said flange at one end of said displacer, said disc means having a central aperture therethrough for metering the flow of mercury into the interior of said displacer wherein said disc means comprises a pair of opposed concave discs having radial peripheral flanges secured together to define a chamber between said discs, said discs having alined central apertures therethrough of diierent crosssectional area.

4. A mercury relay comprising a cup-shaped metal envelope having an enlarged open end, an insulating plug seated in said end and having an axial bore, a tubular electrode extending through said bore and having a lateral opening inwardly of the inner end of said plug, an arc-resisting metal Contact element secured to the inner end of said electrode, sealing means compressed about said electrode and against the outer face of said plug, compression means for locking said sealing means in position, a body of mercury in said envelope normally disposed out of contact with said element, a tubular displacer in said envelope, and coil means surrounding the lower end of said envelope for drawing said displacer down into said mercury to raise the mercury into contact with said element.

5. The relay of claim 4 wherein said electrode comprises a pair of tubulations having one end flared, discs secured about said ared ends, said discs being secured together to form axial continuity of said tubulations, and a recess in the outer face of said plug forming a seat for said discs.

6. The relay of claim 4 wherein said tubulation is employed for evacuating and then lling said envelope with an inert gas under pressure, the outer end of said tubulation being then flattened and welded, and a metal sleeve surrounding said outer end of said electrode and seated in said compression means, and a conductor connected to said flattened end within said sleeve.

7. The relay of claim 4 further characterized in the provision of va disc closing the lower end of said displacer and apertured to meter the ow of mercury therethrough to said element upon energization of said coil means.

8. A mercury relay comprising a tubular metal envelope closed at one end, an insulating plug sealed in the opposite end, a body of mercury in said envelope, an electrode extending through said plug into the interior of said envelope and terminating above the level of said mercury, a tubular displacer surrounding said electrode and having a closed lower end, an aperture in said end, and la magnetic coil surrounding the lower end of said envelope operable when energized to draw said displacer downwardly into said mercury for forcing mercury through said aperture into contact with said electrode.

9. A displacer for a relay of the class described comprising a tubular sleeve, `and a time delay element closing one end of said sleeve including opposed concave discs secured together at their peripheries to dene a chamber therebetween, an aperture in the upper disc of a diameter greater than the meniscus height of mercury, an aperture in the lower disc of a diameter smaller than the meniscus height of mercury, and a body of mercury in said chamber.

l0. The displacer of claim 9 wherein said sleeve comprises a metal sleeve having an inturned radial flange at its lower end forming a shoulder for receiving said disc peripheries, and an insulating bushing in said sleeve maintaining said .disc against movement.

11. A displacer for a mercury relay comprising a tubular sleeve, and a time delay element closing one end of said sleeve including opposed concave discs secured together at their peripheries to define a chamber therebetween, said discs having axially alined apertures of diierent size, and a body of mercury retained in said chamber.

12. A displacer according to claim 11 wherein at least one oi said apertures is of a diameter 10 less than the meniscus height of mercury.

UNO C. HEDIN. 

